1. Field of the Invention
The present invention is directed to a regulator for regulating the flow of ink from an ink source to a print head in a printer; and, more particularly, to a regulator that is submersible within an ink reservoir and that operates relatively independent of the inlet ink pressure.
2. Background of the Invention
The flow of fluids through predetermined conduits has been generally been accomplished using a valve and/or a pressure source. More specifically, valves come in various shapes and sizes and include as a subset, check valves. These valves prevent the reversal of fluid flow from the direction the fluid passed by the valve. A limitation of check valves is that the volumetric flow of the fluid past the valve is controlled by the inlet side fluid pressure. If the inlet pressure is greater than the outlet pressure, the valve will open and fluid will pass by the valve; if not, the inlet fluid will be relatively stagnant and the valve will not open.
Inkjet printers must take ink from an ink source and direct the ink to the print head where the ink is selectively deposited onto a substrate to form dots comprising an image discernable by the human eye. Two general types of systems have been developed for providing the pressure source to facilitate movement of the ink from the ink source to the print head. These generally include gravitational flow system and pumping systems. Pumping systems as the title would imply create an artificial pressure differential between the ink source and the print head to pump the fluid from the ink source to the print head. Generally, these pumping systems have many moving parts and need complex flow control system operatively coupled thereto. Gravitational flow avoids many of these moving parts and complex systems.
Gravitational fluid flow is the most common way of delivering ink from an ink reservoir to a print head for eventual deposition onto a substrate, especially when the print head includes a carrier for the ink source. However, this gravitational flow may cause a problem in that excess ink is allowed to enter the print head and accumulate, being thereafter released or deposited onto an unintended substrate or onto one or more components of the inkjet printer. Thus, the issue of selective control of ink flow from a gravitational source has also relied upon the use of valves. As discussed above, a check valve has not unitarily been able to solve the problems of regulating ink flow, at least in part because the inlet pressure varies with atmospheric pressure, and when the valve is submerged, the pressure exerted by the fluid itself.
U.S. Pat. No. 6,422,693, entitled xe2x80x9cInk Interconnect Between Print Cartridge and Carriagexe2x80x9d, assigned to Hewlett-Packard Company, describes an internal regulator for a print cartridge that regulates the pressure of the ink chamber within the print cartridge. The regulator design includes a plurality of moving parts having many complex features. Thus, there is a need for a regulator to regulate the flow of ink from an ink source to a print head that includes fewer moving parts, that is relatively easy to manufacture and assemble, that is submersible within an ink source without necessitating direct coupling to the atmosphere to properly function.
The invention is directed to a mechanical device providing control over the flow of a fluid from a fluid source to at least a point of accumulation. More specifically, the invention is directed to an ink flow regulator that selectively allows fluid communication between the ink source and the print head so as to supply the print head with ink, while substantially inhibiting the free flow through of print head. The invention comprises a pressurized chamber, generally exhibiting negative gauge pressure therewithin, having an ink flow inlet and an ink flow outlet. A seal is biased against the ink inlet to allow selective fluid communication between the interior of the pressurized chamber and an ink source. A flexible wall, acting as a diaphragm, is integrated with a chamber wall to selectively expand outwardly from and contract inwardly towards the interior of the chamber depending upon the relative pressure differential across the flexible wall. The pressure differential depends upon the pressure of the interior of the chamber verses the pressure on the outside of the flexible wall. Operability of the invention is not negated by having the invention partially submerged or fully submerged beneath a fluid, nor is operability inhibited by having a liquid or a gas contacting the exterior of the flexible wall.
As the flexible wall contracts inwardly toward the interior of the chamber, it actuates a lever. The lever includes a sealing arm and an opposing flexible arm, and pivots on a fulcrum. The sealing arm includes the seal biased against the ink inlet, while the flexible arm is angled with respect to the sealing arm and includes a spoon-shaped end contacting the flexible wall. As the flexible wall continues contracting inward, the flexible arm flexes without pivoting the lever until the force of the wall against the flexible arm is sufficient to overcome the bias biasing the sealing arm against the inlet. When the force against the lever is sufficient to overcome the bias, the lever pivots about the fulcrum to release the seal at the ink inlet, thereby allowing ink to flow into the chamber until the pressure differential is reduced such that the bias again overcomes the reduced push created by the inward contraction of the flexible wall.
It is noted that the invention is not a check valve, as the operation of the regulator is independent from the inlet pressure when the regulator is not submerged within a liquid, and minimally dependent upon inlet pressure when the regulator is submerged within a liquid. In other words, a check valve is wholly dependent upon the inlet pressure, whereas this system of the present invention provides a relatively small inlet cross sectional area in relation to the size and relative forces action upon the regulator system that effectively negates any variance in inlet pressure. Thus, increasing the inlet pressure does not affect the operation of the regulator.
It is a first aspect of the present invention to provide a print head and regulator assembly for a printer that includes: (a) a print head; (b) an ink source; and, (c) a regulator for regulating the flow of ink between the ink source and the print head, the regulator including: (i) a pressurized chamber having an ink inlet in fluid communication with the ink source, an ink outlet in fluid communication with the print head,an opening extending through a chamber wall, and a flexible film covering the opening, the flexible film having an inner surface facing an interior of the pressurized chamber and an outer surface in contact with a liquid; and, (ii) a lever including a flexible arm positioned in proximity to the inner surface of the flexible film and an opposing arm operatively coupled to a seal that closes the ink inlet when the lever is in a first position and opens the ink inlet when the lever is pivoted to a second position; where the lever is biased to the first position; where a higher pressure differential across the flexible film brings about a higher force acting upon the flexible arm to overcome the bias and pivot the lever to the second position opening the ink inlet; and where a lower pressure differential across the flexible film brings about a lesser force acting upon the flexible arm resulting in the lever succumbing to the bias and repositioning the seal at the first position, closing the ink inlet.
In a more detailed embodiment of the first aspect, the ink source is an ink reservoir, and the regulator is at least partially submerged within the ink reservoir and the liquid contacting the outer surface of the flexible film is ink within the ink reservoir.
In another more detailed embodiment, the operating pressure on the interior of the pressurized chamber is between about 5 centimeters water column negative pressure and about 20 centimeters water column negative pressure In a further detailed embodiment, the volume of ink exiting the pressurized chamber between sequential occurrences of the lever pivoting to the second position ranges from about 0.1 mL and about 1.5 mL. In still a further detailed embodiment, the ink inlet is operatively coupled to a siphon tube in fluid communication with the ink source. In yet another detailed embodiment, the flexible film contacts and spatially conforms to the shape of the flexible arm between the first and second positions. In an additional detailed embodiment, the flexible film is a non-elastomeric film. In another detailed embodiment, the regulator is fully submerged within the ink reservoir. In still another detailed embodiment, the lever is biased to the first position by a spring, and the spring constant is dependent upon a depth of submersion of the regulator within the ink reservoir.
It is a second aspect of the present invention to provide an ink cartridge that includes: (a) at least one ink reservoir; and, (b) at least one regulator for regulating the flow of ink between the ink reservoir and an ink cartridge outlet, the regulator including: (i) a pressurized chamber having an ink inlet in fluid communication with the ink reservoir, an ink outlet in fluid communication with the ink cartridge outlet, an opening extending through a chamber wall, and a flexible film covering the opening, the flexible film having an inner surface facing an interior of the pressurized chamber and an outer surface in contact with a liquid; and, (ii) a lever including a flexible arm positioned in proximity to the inner surface of the flexible film and an opposing arm operatively coupled to a seal that closes the ink inlet when the lever is in a first position and opens the ink inlet when the lever is pivoted to a second position, the lever being biased to the first position; where a higher pressure differential across the flexible film brings about a higher force acting upon the flexible arm to overcome the bias and pivot the lever to the second position opening the ink inlet; and where a lower pressure differential across the flexible film brings about a lesser force acting upon the flexible arm resulting in the lever succumbing to the bias and repositioning the seal at the first position, closing the ink inlet.
In a more detailed embodiment of the second aspect, the regulator is at least partially submerged within the ink reservoir such that the liquid contacting the outer surface of the flexible film is ink within the ink reservoir. In another more detailed embodiment, the operating pressure on the interior of the pressurized chamber is between about 5 centimeters water column negative pressure and about 20 centimeters water column negative pressure. In a further detailed embodiment, the volume of ink exiting the pressurized chamber between sequential occurrences of the lever pivoting to the second position ranges from about 0.1 mL and about 1.5 mL. In still a further detailed embodiment, the ink inlet is operatively coupled to a siphon tube in fluid communication with the ink source. In yet another detailed embodiment, the flexible film is a non-elastomeric film. In an additional detailed embodiment, the flexible film contacts and spatially conforms to the shape of the flexible arm between the first and second positions. In a more detailed embodiment, the lever is biased to the first position by a spring, and the spring constant is dependent upon a depth of submersion of the regulator within the ink reservoir. In another detailed embodiment, the ink cartridge includes a plurality of the ink reservoirs and a respective plurality of the regulators at least partially submerged within respective ink reservoirs. In still another detailed embodiment, the regulator is fully submerged within the ink reservoir.
It is a third aspect of the present invention to provide a method of regulating the flow of ink from an ink source to a print head nozzle comprising the steps of: (a) positioning an ink regulator having a pressurized chamber in fluid communication with an ink stream between an ink source and a print head; (b) contacting a flexible wall of the ink regulator with a liquid responsive to a pressure exerted upon ink upstream from the ink regulator; (c) actuating the flexible wall in response to a pressure differential across the flexible wall between a fluid inside the pressurized chamber and the liquid; and, (d) opening or closing at least one valve selectively in response to actuation of the flexible wall to provide fluid communication between a first point an a second point of the ink stream.
In a more detailed embodiment of the third aspect, the positioning step includes the step of submerging, at least partially, the ink regulator within the ink source such that the liquid contacting the flexible wall of the ink regulator is ink in the ink source. In a further detailed embodiment, an additional step includes pivoting a lever in response to the actuating step to open the valve, where the valve is biased closed and resists the lever pivoting. In still a further detailed embodiment, the operating pressure of the pressurized chamber is between about 5 centimeters water column negative pressure and about 20 centimeters water column negative pressure In yet another detailed embodiment, the flexible wall is a non-elastomeric film bonded over an opening in the pressurized chamber. In an additional detailed embodiment, the volume of ink exiting the pressurized chamber between sequential opening of the valve ranges from about 0.1 mL and about 1.5 mL. In a more detailed embodiment, the valve is biased to a closed position and the method further includes the step of correlating the bias of the valve with a depth of submersion of the ink regulator within the ink source.